Why are gases used inside car tires?

Some experts say that using nitrogen has a slower leak ratio than regular air. The air from the local gas station is about 75% Nitrogen and 25% Oxygen at the cost of about $0.75, where a Nitrogen station could cost upwards of $10 per tire or more. Pure nitrogen also doesn't contain moisture that could come from the local fill up station, resulting in having no water taking up space of the air. Water can't be compress so it takes up space in your tire.